Question 1

What was the COBE satellite designed to measure?

Accepted Answer

A)  redshifts of objects at cosmological distances to obtain an accurate measurement of Hubble's constant 
B)  21-cm radio radiation from intergalactic hydrogen 
C)  X rays from quasars and other objects at cosmological distances 
D)  cosmic microwave background radiation 
A)  redshifts of objects at cosmological distances to obtain an accurate measurement of Hubble's constant 
B)  21-cm radio radiation from intergalactic hydrogen 
C)  X rays from quasars and other objects at cosmological distances 
D)  cosmic microwave background radiation

Question 2

Why was the actual measurement of the cosmic microwave background so difficult?

Accepted Answer

A)  Earth's atmosphere is almost opaque in the region of the spectrum where this radiation peaks (long-wavelength infrared/short wavelength microwaves). 
B)  It was never clear where in the spectrum this radiation would fall. 
C)  Because the radiation has spread out so much since its origin in the Big Bang, it is extremely faint. 
D)  The predicted frequency for this radiation was in a range not previously detected, so specialized equipment had to be designed and built. 
A)  Earth's atmosphere is almost opaque in the region of the spectrum where this radiation peaks (long-wavelength infrared/short wavelength microwaves). 
B)  It was never clear where in the spectrum this radiation would fall. 
C)  Because the radiation has spread out so much since its origin in the Big Bang, it is extremely faint. 
D)  The predicted frequency for this radiation was in a range not previously detected, so specialized equipment had to be designed and built.

Question 3

If the density of matter in the universe turned out to be greater than the critical density,it would imply that the universe is:

Accepted Answer

A)  closed. 
B)  open. 
C)  oscillating. 
D)  contracting. 
A)  closed. 
B)  open. 
C)  oscillating. 
D)  contracting.

Question 4

We detect the slight anisotropy in the cosmic microwave background by making redshift measurements: Wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter.This redshift is a:

Accepted Answer

A)  Doppler shift. 
B)  gravitational redshift. 
C)  cosmological redshift. 
D)  Doppler shift, gravitational redshift, or cosmological redshift since all three are one and the same thing. 
A)  Doppler shift. 
B)  gravitational redshift. 
C)  cosmological redshift. 
D)  Doppler shift, gravitational redshift, or cosmological redshift since all three are one and the same thing.

Question 5

What is our current understanding of the expansion of the universe?

Accepted Answer

A)  The universe is expanding too slowly to overcome its mutual gravitational attraction, and thus it will eventually stop expanding and eventually collapse. 
B)  The universe is expanding at exactly its escape speed. Thus, it will continue to slow forever and stop at an infinite time in the future. 
C)  The universe is expanding at a rate greater than its escape speed. Thus, it will continue to expand forever, slowing constantly, without ever stopping. 
D)  None of the answers is correct. 
A)  The universe is expanding too slowly to overcome its mutual gravitational attraction, and thus it will eventually stop expanding and eventually collapse. 
B)  The universe is expanding at exactly its escape speed. Thus, it will continue to slow forever and stop at an infinite time in the future. 
C)  The universe is expanding at a rate greater than its escape speed. Thus, it will continue to expand forever, slowing constantly, without ever stopping. 
D)  None of the answers is correct.

Question 6

When a high-energy gamma-ray photon collides with a nucleus,the gamma-ray photon:

Accepted Answer

A)  produces a huge number of low-energy photons. 
B)  disappears completely, leaving nothing behind. 
C)  disappears, creating a particle-antiparticle pair. 
D)  disappears, creating two negative electrons. 
A)  produces a huge number of low-energy photons. 
B)  disappears completely, leaving nothing behind. 
C)  disappears, creating a particle-antiparticle pair. 
D)  disappears, creating two negative electrons.

Question 7

When the Big Bang began,all the fundamental forces were unified and behaved like a single force.As the universe expanded and cooled during the Big Bang,when did the strong nuclear force first become a separate force?

Accepted Answer

A)  at the start of quark confinement, when the universe was about 10-⁶ s old 
B)  when pair production ceased, when the universe was about 1 s old 
C)  at the Planck time, when the universe was about 10-⁴³ s old 
D)  at the start of the inflationary period, when the universe was about 10-³⁵ s old 
A)  at the start of quark confinement, when the universe was about 10-⁶ s old 
B)  when pair production ceased, when the universe was about 1 s old 
C)  at the Planck time, when the universe was about 10-⁴³ s old 
D)  at the start of the inflationary period, when the universe was about 10-³⁵ s old

Question 8

What is the ratio of cosmic microwave background photons to hydrogen atoms,on average,in our universe?

Accepted Answer

A)  about 1 billion to 1 
B)  about 1 million to 1 
C)  about 1 to 100-very few microwave photons 
D)  about 1 to 1-equal numbers of photons and H atoms 
A)  about 1 billion to 1 
B)  about 1 million to 1 
C)  about 1 to 100-very few microwave photons 
D)  about 1 to 1-equal numbers of photons and H atoms

Question 9

In the present universe,the "mass density" of radiation,using Einstein's equation E = mc² for the photons,is:

Accepted Answer

A)  essentially zero since there is very little radiation left in the universe at the present time. 
B)  much greater than the mass density of matter leading to a radiation-dominated universe. 
C)  equal to the mass density of matter since these parameters have remained balanced throughout the evolution of the universe as a consequence of the equipartition of energy. 
D)  much less than the mass density of matter, leading to a matter-dominated universe. 
A)  essentially zero since there is very little radiation left in the universe at the present time. 
B)  much greater than the mass density of matter leading to a radiation-dominated universe. 
C)  equal to the mass density of matter since these parameters have remained balanced throughout the evolution of the universe as a consequence of the equipartition of energy. 
D)  much less than the mass density of matter, leading to a matter-dominated universe.

Question 10

The future of the overall universe,in terms of its ultimate evolution and whether it will expand forever or eventually contract again,is determined by which of its parameters?

Accepted Answer

A)  the present volume of the universe 
B)  the amount of matter and energy within it 
C)  the intensity of cosmic microwave background radiation 
D)  the temperature of the gas within it 
A)  the present volume of the universe 
B)  the amount of matter and energy within it 
C)  the intensity of cosmic microwave background radiation 
D)  the temperature of the gas within it

Question 11

When the universe was about 2500 years old,the radiation density had decreased to the point where it was equal to the matter density.Yet it was only many years later that atoms formed.What happened to make possible the formation of atoms?

Accepted Answer

A)  The average photon energy decreased until it could no longer ionize hydrogen. 
B)  Radiation pressure decreased until it was equal to the inward pressure due to gravity. 
C)  The temperature reached the point where the reaction 4 ¹H → ⁴He could proceed. 
D)  Neutrons decayed to produce protons and electrons, the building blocks of atoms. 
A)  The average photon energy decreased until it could no longer ionize hydrogen. 
B)  Radiation pressure decreased until it was equal to the inward pressure due to gravity. 
C)  The temperature reached the point where the reaction 4 ¹H → ⁴He could proceed. 
D)  Neutrons decayed to produce protons and electrons, the building blocks of atoms.

Question 12

In which universe scenario will the present universe evolve to a Big Crunch at some time in the future?

Accepted Answer

A)  an open universe 
B)  a Newtonian universe 
C)  a closed universe 
D)  a flat universe 
A)  an open universe 
B)  a Newtonian universe 
C)  a closed universe 
D)  a flat universe

Question 13

Which parameter of the present universe is considered to be critical in determining the ultimate fate of the universe?

Accepted Answer

A)  the amount of mass in black holes in the universe 
B)  the number of neutrinos in the universe 
C)  the amount of matter and energy in the universe 
D)  the number of photons of radiation in the universe 
A)  the amount of mass in black holes in the universe 
B)  the number of neutrinos in the universe 
C)  the amount of matter and energy in the universe 
D)  the number of photons of radiation in the universe

Question 14

When did the universe cool to a temperature of 3 K?

Accepted Answer

A)  1 second after the start of the Big Bang, when pair production ceased 
B)  500,000 years after the Big Bang, when the universe became transparent to radiation 
C)  3 minutes after the start of the Big Bang, when primordial nuclear reactions ceased 
D)  very recently 
A)  1 second after the start of the Big Bang, when pair production ceased 
B)  500,000 years after the Big Bang, when the universe became transparent to radiation 
C)  3 minutes after the start of the Big Bang, when primordial nuclear reactions ceased 
D)  very recently

Question 15

How does the cosmological constant differ from quintessence?

Accepted Answer

A)  The cosmological constant is a specific physical effect that can be described mathematically, whereas quintessence is the total of all indefinable properties that make the universe what it is at any given time. 
B)  The cosmological constant provides an accelerating force in the universal expansion, whereas quintessence provides a decelerating term; it is the balance between the cosmological constant and quintessence that determines whether the expansion accelerates or decelerates. 
C)  There is essentially no difference; basically, quintessence is the modern name for the cosmological constant. 
D)  The cosmological constant provides a constant accelerating force in the universal expansion, whereas quintessence can change as the expansion proceeds. 
A)  The cosmological constant is a specific physical effect that can be described mathematically, whereas quintessence is the total of all indefinable properties that make the universe what it is at any given time. 
B)  The cosmological constant provides an accelerating force in the universal expansion, whereas quintessence provides a decelerating term; it is the balance between the cosmological constant and quintessence that determines whether the expansion accelerates or decelerates. 
C)  There is essentially no difference; basically, quintessence is the modern name for the cosmological constant. 
D)  The cosmological constant provides a constant accelerating force in the universal expansion, whereas quintessence can change as the expansion proceeds.

Question 16

The photons that enter our microwave detectors today (and that we interpret as the cosmic microwave background radiation)had their last interaction with matter:

Accepted Answer

A)  at the instant of the Big Bang. 
B)  during the inflationary epoch. 
C)  during the era of recombination. 
D)  at the time of symmetry breaking. 
A)  at the instant of the Big Bang. 
B)  during the inflationary epoch. 
C)  during the era of recombination. 
D)  at the time of symmetry breaking.

Question 17

According to Hubble's law,how old is the universe (H₀ = Hubble's constant)?

Accepted Answer

A)  v/H₀ (where v = recession velocity in km/s) 
B)  r/H₀ (where r = distance in Mpc) 
C)  H₀ 
D)  1/H₀ 
A)  v/H₀ (where v = recession velocity in km/s) 
B)  r/H₀ (where r = distance in Mpc) 
C)  H₀ 
D)  1/H₀

Question 18

What is the period of quark confinement?

Accepted Answer

A)  Because of the very large pressure in early times, all the quarks were confined to a small volume. After the inflationary, epoch the pressure dropped and the quarks were able to spread out to assume the distribution we find today. 
B)  During the period of quark confinement, the energy of the photons was sufficiently high that conglomerations of quarks, such as neutrons and protons, could not exist and quarks were free. 
C)  During the period of quark confinement, the energy of the photons was sufficiently low that conglomerations of quarks, such as neutrons and protons, could exist without being blasted apart as soon as they were formed. 
D)  The period of quark confinement was the very early period in the universe when all matter and energy were confined to a region the size of a single quark. 
A)  Because of the very large pressure in early times, all the quarks were confined to a small volume. After the inflationary, epoch the pressure dropped and the quarks were able to spread out to assume the distribution we find today. 
B)  During the period of quark confinement, the energy of the photons was sufficiently high that conglomerations of quarks, such as neutrons and protons, could not exist and quarks were free. 
C)  During the period of quark confinement, the energy of the photons was sufficiently low that conglomerations of quarks, such as neutrons and protons, could exist without being blasted apart as soon as they were formed. 
D)  The period of quark confinement was the very early period in the universe when all matter and energy were confined to a region the size of a single quark.

Question 19

When the intensity of the cosmic microwave background radiation is plotted against wavelength,what is the shape of the resulting curve?

Accepted Answer

A)  emission lines, strongest and most densely concentrated in the microwave region 
B)  a composite of many overlapping blackbody curves from gas clouds of different temperatures peaking in the microwaves 
C)  a blackbody curve modified by many deep, overlapping absorption lines and several emission lines 
D)  an essentially perfect blackbody spectrum peaking in the microwave region 
A)  emission lines, strongest and most densely concentrated in the microwave region 
B)  a composite of many overlapping blackbody curves from gas clouds of different temperatures peaking in the microwaves 
C)  a blackbody curve modified by many deep, overlapping absorption lines and several emission lines 
D)  an essentially perfect blackbody spectrum peaking in the microwave region

Question 20

Why can virtual particles exist for only a very short length of time?

Accepted Answer

A)  Virtual particles by their nature have very little energy and thus cannot move very far before they stop. 
B)  If the particles existed longer than this short length of time, the law of conservation of energy would be violated because real energy would appear from nowhere. 
C)  If this limited time were exceeded, there would be too many virtual particles in existence at one time, which would violate the Pauli exclusion principle of one particle per set of quantum numbers. 
D)  Virtual-particle pairs were created only during the era of cosmic inflation and lasted a mere 10-³² s. 
A)  Virtual particles by their nature have very little energy and thus cannot move very far before they stop. 
B)  If the particles existed longer than this short length of time, the law of conservation of energy would be violated because real energy would appear from nowhere. 
C)  If this limited time were exceeded, there would be too many virtual particles in existence at one time, which would violate the Pauli exclusion principle of one particle per set of quantum numbers. 
D)  Virtual-particle pairs were created only during the era of cosmic inflation and lasted a mere 10-³² s.

What was the COBE satellite designed to measure?

Why was the actual measurement of the cosmic microwave background so difficult?

If the density of matter in the universe turned out to be greater than the critical density,it would imply that the universe is:

We detect the slight anisotropy in the cosmic microwave background by making redshift measurements: Wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter.This redshift is a:

What is our current understanding of the expansion of the universe?

When a high-energy gamma-ray photon collides with a nucleus,the gamma-ray photon:

When the Big Bang began,all the fundamental forces were unified and behaved like a single force.As the universe expanded and cooled during the Big Bang,when did the strong nuclear force first become a separate force?

What is the ratio of cosmic microwave background photons to hydrogen atoms,on average,in our universe?

In the present universe,the "mass density" of radiation,using Einstein's equation E = mc² for the photons,is:

The future of the overall universe,in terms of its ultimate evolution and whether it will expand forever or eventually contract again,is determined by which of its parameters?

When the universe was about 2500 years old,the radiation density had decreased to the point where it was equal to the matter density.Yet it was only many years later that atoms formed.What happened to make possible the formation of atoms?

In which universe scenario will the present universe evolve to a Big Crunch at some time in the future?

Which parameter of the present universe is considered to be critical in determining the ultimate fate of the universe?

When did the universe cool to a temperature of 3 K?

How does the cosmological constant differ from quintessence?

The photons that enter our microwave detectors today (and that we interpret as the cosmic microwave background radiation)had their last interaction with matter:

According to Hubble's law,how old is the universe (H₀ = Hubble's constant)?

What is the period of quark confinement?

When the intensity of the cosmic microwave background radiation is plotted against wavelength,what is the shape of the resulting curve?

Why can virtual particles exist for only a very short length of time?

Discovering the Night Sky

Gravitation and the Waltz of the Planets

Light and Telescopes

Formation of the Solar System and Other Planetary Systems

Exoplanets

The Terrestrial Planets and Their Moons

The Outer Planets and Their Moons

Vagabonds of the Solar System

The Sun: Our Extraordinary Ordinary Star

Characterizing Stars

The Lives of the Stars From Birth Through Middle Age

The Deaths and Remnants of Stars

The Galaxies

Astrobiology

Filters

Exam 14: Cosmology

What was the COBE satellite designed to measure?

Why was the actual measurement of the cosmic microwave background so difficult?

If the density of matter in the universe turned out to be greater than the critical density,it would imply that the universe is:

We detect the slight anisotropy in the cosmic microwave background by making redshift measurements: Wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter.This redshift is a:

What is our current understanding of the expansion of the universe?

When a high-energy gamma-ray photon collides with a nucleus,the gamma-ray photon:

When the Big Bang began,all the fundamental forces were unified and behaved like a single force.As the universe expanded and cooled during the Big Bang,when did the strong nuclear force first become a separate force?

What is the ratio of cosmic microwave background photons to hydrogen atoms,on average,in our universe?

In the present universe,the "mass density" of radiation,using Einstein's equation E = mc² for the photons,is:

The future of the overall universe,in terms of its ultimate evolution and whether it will expand forever or eventually contract again,is determined by which of its parameters?

When the universe was about 2500 years old,the radiation density had decreased to the point where it was equal to the matter density.Yet it was only many years later that atoms formed.What happened to make possible the formation of atoms?

In which universe scenario will the present universe evolve to a Big Crunch at some time in the future?

Which parameter of the present universe is considered to be critical in determining the ultimate fate of the universe?

When did the universe cool to a temperature of 3 K?

How does the cosmological constant differ from quintessence?

The photons that enter our microwave detectors today (and that we interpret as the cosmic microwave background radiation)had their last interaction with matter:

According to Hubble's law,how old is the universe (H₀ = Hubble's constant)?

What is the period of quark confinement?

When the intensity of the cosmic microwave background radiation is plotted against wavelength,what is the shape of the resulting curve?

Why can virtual particles exist for only a very short length of time?

Discovering the Night Sky

Gravitation and the Waltz of the Planets

Light and Telescopes

Formation of the Solar System and Other Planetary Systems

Exoplanets

The Terrestrial Planets and Their Moons

The Outer Planets and Their Moons

Vagabonds of the Solar System

The Sun: Our Extraordinary Ordinary Star

Characterizing Stars

The Lives of the Stars From Birth Through Middle Age

The Deaths and Remnants of Stars

The Galaxies

Astrobiology

Filters